President Obama's dream of dramatically remaking the nation's health-care system is still a long way from reality. But if lawmakers can reach an accord, one thing is virtually certain: For the first time ever, every American would be required to carry health insurance.

The requirement, known as an individual mandate, is among the most far-reaching changes envisioned this year by those pushing for health-care reform. And it is one of the few common threads running through all three bills being considered in Congress, greatly increasing the likelihood it will survive the legislative process. Obama continued Tuesday to push lawmakers struggling with the large costs and scope of health legislation to move forward, pronouncing reform to be "closer than ever."

Just as drivers must purchase auto insurance, the medical system of the future would put responsibility for health coverage first and foremost on every adult.

For the vast majority of Americans who have health insurance, the change would mean little more than submitting a form with their tax returns proving that the plan they carry meets certain minimum standards. Many of the nation's 47 million uninsured people, however, would be required to purchase a health policy or face financial penalties, though waivers or discounts would be provided for lower-income Americans.

The concept is modeled after a requirement instituted in Massachusetts three years ago as part of that state's broad health-care overhaul. And like the Massachusetts law, the individual mandate proposed by congressional Democrats would be paired with a much more controversial new requirement that nearly every employer contribute to the total cost of care.

"Without an individual mandate, you're never going to get to universal coverage," said Bradley Herring, a health economist at Johns Hopkins University.

Bringing everyone into the insurance pool -- particularly young, healthy customers -- spreads the risk and lowers overall costs. "That will make it more affordable for everyone," Herring said.

Some proponents of a European-style, nationalized single-payer approach say an individual mandate places an unfair financial burden on lower-income consumers. Some conservative analysts argue that such a requirement forces individuals into an overpriced, underperforming health system.

Yet in a nation that prides itself on having freedom of choice, it is striking that such a wide and diverse coalition has formed around the individual mandate. Labor unions, economists, the medical industry, big business, some prominent Republicans and Obama all support the requirement, which has its roots in the conservative philosophy of self-reliance.

In the debate over Massachusetts's measure, then-Gov. Mitt Romney, a Republican with presidential aspirations, touted the approach as a "personal responsibility system."

Hospitals, insurers and drug manufacturers -- salivating at the prospect of up to 50 million newly insured customers -- have lobbied ferociously for the federal provision.

Obama, after sparring last year with his Democratic presidential primary opponents over the concept, is a convert, as long as there are "hardship exemptions" for those least able to pay.